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Jan Trnka

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Universitas Katolik Parahyangan

University of Cagliari

Armando Marques-Guedes

UNL - New University of Lisbon

Iolanda Craifaleanu

Technical University Of Civil Engineering, Bucharest

Franco Bontempi

Università degli Studi "La Sapienza" di Roma

Fabián Hoyos Patiño

Universidad Nacional de Colombia (National University of Colombia)

Universidad del Norte - Barranquilla, Colombia

Visvesvaraya Technological University

Flavio Stochino

University of Cagliari

Richard Crawford

The University of Texas at Austin

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Papers by Jan Trnka

Effect of the loading rate on compressive properties of goose eggs

Journal of Biological Physics, Oct 27, 2015

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the... more The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.

Shock waves in mechanics of fluid and solids studied by double pulse holointerferometry

Vibrations of human skull studied by holo-interferometry

The paper deals with an application of holointerferometry to the biomechanical investigation of t... more The paper deals with an application of holointerferometry to the biomechanical investigation of the part of the human sound conducting system. The human skull was periodically loadet by the different types of vibrators. The resonant mode of the skull vibrations were studied by a usual time-average holointerferometry

AE a DPHI při studiu geometrické disperze tenkých, izotropních válcových skořepin

Optical Interferometry Methods Used to Study Interaction of Acoustical Waves with Structural Inhomogenities

Poster is concerned with the scattering of Lamb waves mode A0 in the surrouding of structural inh... more Poster is concerned with the scattering of Lamb waves mode A0 in the surrouding of structural inhomogenities in thin plates. The transient state is caused by different way of generating of ultrashort impact loading. The responses are detected by both full-field and pointwise optical methods. We show results of Double-Pulse Holointerferometry, Electonic Speckle Patterns Interferometry and Laservibrometry.

Response of the Ostrich Eggshell to Non Destructive Impact

An experimental system was set up to generate the impact force, measure the response wave signal,... more An experimental system was set up to generate the impact force, measure the response wave signal, and analyse the frequency spectrum for physical properties detection of biological product. The dynamic resonance frequency of egg was obtained through the analysis of the dynamically measured frequency response of an egg excited by pendulum. The effects of excitation point, detected point and impact intensity on the dominant frequency were analysed.

Time and Frequency Domain Response of Grape Berries to Nondestructive Impact during the Harvesting Period

Journal of Texture Studies, 2015

An experimental system was set up to generate the impact force, measure the response wave signal ... more An experimental system was set up to generate the impact force, measure the response wave signal and analyze the frequency spectrum for detection of the behavior of grape berries at different harvest days. Seven varieties of grape berries harvested for six consecutive weeks have been tested. The response of grape berries to a nondestructive impact is studied both in time and in frequency domains. The digitalized time history of the force was analyzed to extract some mechanical characteristics (peak force, impact duration, impulse). The evaluation of the modulus of elasticity of berries using frequency response characteristics was carried out. This modulus decreases with the total sugar content. This dependence can be used for the estimation of the maturity of grape berries. PRACTICAL APPLICATIONS This paper describes the use of a technique of the nondestructive impact for monitoring grape texture, particularly during ripening. It was found that the response of the grape berries to this impact measured as the time history of the surface displacement provided reliable tool to monitor the progress of grape maturity. The described method could also be used to highlight important information on grape evolution during ripening including their composition (total sugar content) and help to provide better insight on the choice of the preferred/ ideal harvest date. Owing to the available computer techniques, this method enables testing much more number of berries in comparison with classical methods of the evaluation of grape's mechanical properties.

Wave motion in fibre-reinforced thin orthotropic laminate

Acta technica ČSAV, 2007

Résumé/Abstract Wave propagation in a fibre-reinforced thin orthotropic laminate is studied in th... more

Dynamic Behavior of PE-HD Pipes Grade

Macromolecular Symposia, 2017

The split Hopkinson pressure bar test is extensively used to characterize material at high strain... more The split Hopkinson pressure bar test is extensively used to characterize material at high strain rate. This method enables to evaluate strain, strain rate and stress in the specimen. The viscoelastic behavior of materials in study was described using of the complex elastic modulus. Three copolymers of high-density polyethylene (PE-HD) have been investigated, two unimodal types supplied by two chemical companies and one bimodal type. Structure of PE samples (pellets) was characterised by 13 C NMR (Carbon-13 nuclear magnetic resonance).

Behavior of cracked eggs at non-destructive impact

Behaviour of eggshell membranes at tensile loading

The aim of this paper was to study the mechanical behaviour of the eggshell membrane using tensil... more The aim of this paper was to study the mechanical behaviour of the eggshell membrane using tensile tests at different loading rates. The eggshell membrane was obtained from commercial breeding lines of Japanese quails (Coturnix japonica). Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The dependence of the stress on the strain in non-linear region can be described using of the Mooney-Rivlin equation. Linear region corresponds to the elastic strain. Parameters of the used equation are dependent on the strain rate. Generally, the strength of the eggshell membrane increases with the strain rate.

Influence of sugar beet storage duration on root responseto non-destructive impacts

International Agrophysics, 2018

For the purpose of this paper, sugar beet roots were loaded by creating the impact of aluminium b... more For the purpose of this paper, sugar beet roots were loaded by creating the impact of aluminium bars falling from different heights. The time history of the force at the contact between the sugar beet root and the bar was measured. The response of the sugar beet root to the impact was evaluated in terms of surface displacement. This displacement was measured using a laser vibrometer. The displacement was studied in the time and frequency domain during the postharvest period, up to 71 days after crop collection. The measured parameters describing the sugar beet response were significantly sensitive to the storage duration, namely in the frequency domain. Correlations between the storage duration and the main parameters of both the force and surface displacement were identified (p < 0.05).

Behavior of high-density polyethylene at high strain rates

Applied and Computational Mechanics, 2021

The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rate... more The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rates between 102 to 103 s-1. Higher strain rates were achieved using the direct Hopkinson test. Experimental data were evaluated in time as well as in the frequency domain. A more detailed analysis in the frequency domain showed that the description of tested polymers can be described in the framework of the linear viscoelasticity. The use of the direct Hopkinson test showed the occurrence of a permanent strain.

THE IMPULSE RESPONSE METHOD FOR MEASURING THE OVERALL FIRMNESS OF FRUIT HODNOCENÍ PEVNOSTI OVOCE POMOCÍ MĚŘENÍ ODEZVY PŘI IMPULZNÍM ZATĚŢOVÁNÍ Abstract Dynamic resonance frequency based on dynamic frequency response of excited peach

Dynamic resonance frequency based on dynamic frequency response of excited peach was determined b... more Dynamic resonance frequency based on dynamic frequency response of excited peach was determined by peach physical properties, such as, peach firmness, peach mass, and day of harvesting. Analysis showed that dominant frequency increased with peach firmness increasing, and dominant frequency decreased with increasing of the peach mass.

p . 71 – 73 Tensile sTrengTh of Dark ChoColaTe

Chocolate is, in essence, cocoa mass and sugar suspended in a cocoa butter matrix. Cocoa butter h... more Chocolate is, in essence, cocoa mass and sugar suspended in a cocoa butter matrix. Cocoa butter has a distinct texture due to unique interactions of polymorphic lipid structures. In order to describe its texture, it is necessary to evaluate its mechanical properties. These properties are studied using many different experimental methods. A penetration test using a thin probe is an empirical method of assessing the mechanical properties of chocolate or confectionery products (Liang and Hartel, 2004; Do et al., 2007; Afoakwa et al., 2008, 2009). This method has been used to study the effect of composition, particle size distribution, fat crystallization behaviour and tempering on the mechanical properties in chocolate bars (Afoakwa et al., 2008, 2009). Fundamental methods, such as compression and threepoint bend tests, have also been applied to investigate hardness (Beckett, 2000) as well as chocolate texture as a function of composition, fat content or storage conditions (Tscheuschne...

Double pulse holointerferometry and ultrasonic techniques used in study of guided waves propagating in a thin cylindrical shell

Stress wave propagation in thin wall structures is of interest in many areas of applied mechanics... more Stress wave propagation in thin wall structures is of interest in many areas of applied mechanics. The advanced ultrasonic non-destructive testing of shell structures is conditioned by understanding of waves propagating in thin-wall solids. Ultrasonic waves were generated by focusing the pulse laser beam on the surface of the thin cylindrical shell. The full-field visualization of the displacements caused by generated waves was carried out by double-pulse holointerferometry (DPHI) with a ruby laser as a source of light. The second part of the paper is focused on the study of influence of the shell curvature on the wave propagation. This research was carried out by recording the time history of the ultrasonic waves in different points on the shell surface by the pair of miniature piezoelectric transducers. The aim of the paper is to contribute to ultrasonic non-destructive testing of thin shell structures.

Fracture of the Eggshell Under Impact Lom Vaječné Skořápky Při Rázu

Hen’s eggshell behaviour at the impact on a rigid plate is studied. The critical impact velocity ... more Hen’s eggshell behaviour at the impact on a rigid plate is studied. The critical impact velocity at which eggshell damage starts has been determined. This velocity depends on the egg’s shape. LS DYNA 3D finite element code has been used for the evaluation of the stress and strain distribution in the eggshell during its impact. This numerical simulation enables to evaluate the eggshell strength. This strength is independent on the egg shape as well as on the eggshell thickness. It seems that this strength is an intrinsic material parameter. Abstrakt V dané práci byla provedena numerická simulace deformačního a lomového chování vejce při jeho dopadu na tuhou překážku. Byl použit program LS DYNA 3D, který umožňuje modelovat i přítomnost kapaliny a vzduchu uvnitř vaječné skořápky. Ukazuje se, že kritická dopadová rychlost závisí na tvaru vejce. Pevnost vaječné skořápky je pak nezávislá jak na tvaru, tak na tloušťce vaječné skořápky.

Response of Wood Bars to Non-Destructive Impact

Experimental Techniques, 2016

The wood bars with rectangular cross section (25 × 25 mm, 300 mm in length) were impacted by an a... more The wood bars with rectangular cross section (25 × 25 mm, 300 mm in length) were impacted by an aluminum cylindrical bar in R and T directions. The wood response to this loading was characterized by the displacement of the surface of the bar. The time history of this response has been measured by a double channel laser vibrometer. The analysis of response functions was performed both in the time and frequency domain. The bar response to the impact is described using the transfer function. The knowledge of this function enables to predict the surface displacement at the given point for various forces. It is shown that the history of the surface displacement in direction of its propagation exhibits the same qualitative features independently of the kind of wood in the direction of impact and of the position of wave detection. Experiments were performed on bars made from five tree species: Pinus sylvestris L., Picea abies (L.) Karst., Fagus sylvatica, Quercus robur and Populus nigra.

Dynamic Electronic Speckle Pattern Interferometry in Application to Measure Out-Of-Plane Displacement

Electronic Speckle Pattern Interferometry is used to measure out-of-plane dynamic deformations of... more Electronic Speckle Pattern Interferometry is used to measure out-of-plane dynamic deformations of a diffusely scattering object. The fast transient events were excited by an impulsive load caused by focusing high-power laser beam on the surface of a thin steel plate. The fringe pattern representing contours of constant displacement component was revealed by subtraction mode. The object’s surface displacements achieved by using ESPI system and a laser vibrometer are compared.

Tensile Strength of the Eggshell Membranes

Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2016

The mechanical behaviour of eggshell membranes under tensile loading has been studied. Samples fr... more The mechanical behaviour of eggshell membranes under tensile loading has been studied. Samples from different bird species (hen, goose and Japanese quail) have been used. Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The experiments were performed at five loading velocities 1, 10, 100, 400 and 800 mm.min−1. The main parameters describing the eggshell strength increase with the loading rate. This dependence exhibits the same qualitative features as the rate dependence of the eggshell strength.

Effect of the loading rate on compressive properties of goose eggs

Journal of Biological Physics, Oct 27, 2015

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the... more The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.

Shock waves in mechanics of fluid and solids studied by double pulse holointerferometry

Vibrations of human skull studied by holo-interferometry

The paper deals with an application of holointerferometry to the biomechanical investigation of t... more The paper deals with an application of holointerferometry to the biomechanical investigation of the part of the human sound conducting system. The human skull was periodically loadet by the different types of vibrators. The resonant mode of the skull vibrations were studied by a usual time-average holointerferometry

AE a DPHI při studiu geometrické disperze tenkých, izotropních válcových skořepin

Optical Interferometry Methods Used to Study Interaction of Acoustical Waves with Structural Inhomogenities

Poster is concerned with the scattering of Lamb waves mode A0 in the surrouding of structural inh... more Poster is concerned with the scattering of Lamb waves mode A0 in the surrouding of structural inhomogenities in thin plates. The transient state is caused by different way of generating of ultrashort impact loading. The responses are detected by both full-field and pointwise optical methods. We show results of Double-Pulse Holointerferometry, Electonic Speckle Patterns Interferometry and Laservibrometry.

Response of the Ostrich Eggshell to Non Destructive Impact

An experimental system was set up to generate the impact force, measure the response wave signal,... more An experimental system was set up to generate the impact force, measure the response wave signal, and analyse the frequency spectrum for physical properties detection of biological product. The dynamic resonance frequency of egg was obtained through the analysis of the dynamically measured frequency response of an egg excited by pendulum. The effects of excitation point, detected point and impact intensity on the dominant frequency were analysed.

Time and Frequency Domain Response of Grape Berries to Nondestructive Impact during the Harvesting Period

Journal of Texture Studies, 2015

An experimental system was set up to generate the impact force, measure the response wave signal ... more An experimental system was set up to generate the impact force, measure the response wave signal and analyze the frequency spectrum for detection of the behavior of grape berries at different harvest days. Seven varieties of grape berries harvested for six consecutive weeks have been tested. The response of grape berries to a nondestructive impact is studied both in time and in frequency domains. The digitalized time history of the force was analyzed to extract some mechanical characteristics (peak force, impact duration, impulse). The evaluation of the modulus of elasticity of berries using frequency response characteristics was carried out. This modulus decreases with the total sugar content. This dependence can be used for the estimation of the maturity of grape berries. PRACTICAL APPLICATIONS This paper describes the use of a technique of the nondestructive impact for monitoring grape texture, particularly during ripening. It was found that the response of the grape berries to this impact measured as the time history of the surface displacement provided reliable tool to monitor the progress of grape maturity. The described method could also be used to highlight important information on grape evolution during ripening including their composition (total sugar content) and help to provide better insight on the choice of the preferred/ ideal harvest date. Owing to the available computer techniques, this method enables testing much more number of berries in comparison with classical methods of the evaluation of grape's mechanical properties.

Wave motion in fibre-reinforced thin orthotropic laminate

Acta technica ČSAV, 2007

Résumé/Abstract Wave propagation in a fibre-reinforced thin orthotropic laminate is studied in th... more

Dynamic Behavior of PE-HD Pipes Grade

Macromolecular Symposia, 2017

The split Hopkinson pressure bar test is extensively used to characterize material at high strain... more The split Hopkinson pressure bar test is extensively used to characterize material at high strain rate. This method enables to evaluate strain, strain rate and stress in the specimen. The viscoelastic behavior of materials in study was described using of the complex elastic modulus. Three copolymers of high-density polyethylene (PE-HD) have been investigated, two unimodal types supplied by two chemical companies and one bimodal type. Structure of PE samples (pellets) was characterised by 13 C NMR (Carbon-13 nuclear magnetic resonance).

Behavior of cracked eggs at non-destructive impact

Behaviour of eggshell membranes at tensile loading

The aim of this paper was to study the mechanical behaviour of the eggshell membrane using tensil... more The aim of this paper was to study the mechanical behaviour of the eggshell membrane using tensile tests at different loading rates. The eggshell membrane was obtained from commercial breeding lines of Japanese quails (Coturnix japonica). Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The dependence of the stress on the strain in non-linear region can be described using of the Mooney-Rivlin equation. Linear region corresponds to the elastic strain. Parameters of the used equation are dependent on the strain rate. Generally, the strength of the eggshell membrane increases with the strain rate.

Influence of sugar beet storage duration on root responseto non-destructive impacts

International Agrophysics, 2018

For the purpose of this paper, sugar beet roots were loaded by creating the impact of aluminium b... more For the purpose of this paper, sugar beet roots were loaded by creating the impact of aluminium bars falling from different heights. The time history of the force at the contact between the sugar beet root and the bar was measured. The response of the sugar beet root to the impact was evaluated in terms of surface displacement. This displacement was measured using a laser vibrometer. The displacement was studied in the time and frequency domain during the postharvest period, up to 71 days after crop collection. The measured parameters describing the sugar beet response were significantly sensitive to the storage duration, namely in the frequency domain. Correlations between the storage duration and the main parameters of both the force and surface displacement were identified (p < 0.05).

Behavior of high-density polyethylene at high strain rates

Applied and Computational Mechanics, 2021

The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rate... more The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rates between 102 to 103 s-1. Higher strain rates were achieved using the direct Hopkinson test. Experimental data were evaluated in time as well as in the frequency domain. A more detailed analysis in the frequency domain showed that the description of tested polymers can be described in the framework of the linear viscoelasticity. The use of the direct Hopkinson test showed the occurrence of a permanent strain.

THE IMPULSE RESPONSE METHOD FOR MEASURING THE OVERALL FIRMNESS OF FRUIT HODNOCENÍ PEVNOSTI OVOCE POMOCÍ MĚŘENÍ ODEZVY PŘI IMPULZNÍM ZATĚŢOVÁNÍ Abstract Dynamic resonance frequency based on dynamic frequency response of excited peach

Dynamic resonance frequency based on dynamic frequency response of excited peach was determined b... more Dynamic resonance frequency based on dynamic frequency response of excited peach was determined by peach physical properties, such as, peach firmness, peach mass, and day of harvesting. Analysis showed that dominant frequency increased with peach firmness increasing, and dominant frequency decreased with increasing of the peach mass.

p . 71 – 73 Tensile sTrengTh of Dark ChoColaTe

Chocolate is, in essence, cocoa mass and sugar suspended in a cocoa butter matrix. Cocoa butter h... more Chocolate is, in essence, cocoa mass and sugar suspended in a cocoa butter matrix. Cocoa butter has a distinct texture due to unique interactions of polymorphic lipid structures. In order to describe its texture, it is necessary to evaluate its mechanical properties. These properties are studied using many different experimental methods. A penetration test using a thin probe is an empirical method of assessing the mechanical properties of chocolate or confectionery products (Liang and Hartel, 2004; Do et al., 2007; Afoakwa et al., 2008, 2009). This method has been used to study the effect of composition, particle size distribution, fat crystallization behaviour and tempering on the mechanical properties in chocolate bars (Afoakwa et al., 2008, 2009). Fundamental methods, such as compression and threepoint bend tests, have also been applied to investigate hardness (Beckett, 2000) as well as chocolate texture as a function of composition, fat content or storage conditions (Tscheuschne...

Double pulse holointerferometry and ultrasonic techniques used in study of guided waves propagating in a thin cylindrical shell

Stress wave propagation in thin wall structures is of interest in many areas of applied mechanics... more Stress wave propagation in thin wall structures is of interest in many areas of applied mechanics. The advanced ultrasonic non-destructive testing of shell structures is conditioned by understanding of waves propagating in thin-wall solids. Ultrasonic waves were generated by focusing the pulse laser beam on the surface of the thin cylindrical shell. The full-field visualization of the displacements caused by generated waves was carried out by double-pulse holointerferometry (DPHI) with a ruby laser as a source of light. The second part of the paper is focused on the study of influence of the shell curvature on the wave propagation. This research was carried out by recording the time history of the ultrasonic waves in different points on the shell surface by the pair of miniature piezoelectric transducers. The aim of the paper is to contribute to ultrasonic non-destructive testing of thin shell structures.

Fracture of the Eggshell Under Impact Lom Vaječné Skořápky Při Rázu

Hen’s eggshell behaviour at the impact on a rigid plate is studied. The critical impact velocity ... more Hen’s eggshell behaviour at the impact on a rigid plate is studied. The critical impact velocity at which eggshell damage starts has been determined. This velocity depends on the egg’s shape. LS DYNA 3D finite element code has been used for the evaluation of the stress and strain distribution in the eggshell during its impact. This numerical simulation enables to evaluate the eggshell strength. This strength is independent on the egg shape as well as on the eggshell thickness. It seems that this strength is an intrinsic material parameter. Abstrakt V dané práci byla provedena numerická simulace deformačního a lomového chování vejce při jeho dopadu na tuhou překážku. Byl použit program LS DYNA 3D, který umožňuje modelovat i přítomnost kapaliny a vzduchu uvnitř vaječné skořápky. Ukazuje se, že kritická dopadová rychlost závisí na tvaru vejce. Pevnost vaječné skořápky je pak nezávislá jak na tvaru, tak na tloušťce vaječné skořápky.

Response of Wood Bars to Non-Destructive Impact

Experimental Techniques, 2016

The wood bars with rectangular cross section (25 × 25 mm, 300 mm in length) were impacted by an a... more The wood bars with rectangular cross section (25 × 25 mm, 300 mm in length) were impacted by an aluminum cylindrical bar in R and T directions. The wood response to this loading was characterized by the displacement of the surface of the bar. The time history of this response has been measured by a double channel laser vibrometer. The analysis of response functions was performed both in the time and frequency domain. The bar response to the impact is described using the transfer function. The knowledge of this function enables to predict the surface displacement at the given point for various forces. It is shown that the history of the surface displacement in direction of its propagation exhibits the same qualitative features independently of the kind of wood in the direction of impact and of the position of wave detection. Experiments were performed on bars made from five tree species: Pinus sylvestris L., Picea abies (L.) Karst., Fagus sylvatica, Quercus robur and Populus nigra.

Dynamic Electronic Speckle Pattern Interferometry in Application to Measure Out-Of-Plane Displacement

Electronic Speckle Pattern Interferometry is used to measure out-of-plane dynamic deformations of... more Electronic Speckle Pattern Interferometry is used to measure out-of-plane dynamic deformations of a diffusely scattering object. The fast transient events were excited by an impulsive load caused by focusing high-power laser beam on the surface of a thin steel plate. The fringe pattern representing contours of constant displacement component was revealed by subtraction mode. The object’s surface displacements achieved by using ESPI system and a laser vibrometer are compared.

Tensile Strength of the Eggshell Membranes

Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2016

The mechanical behaviour of eggshell membranes under tensile loading has been studied. Samples fr... more The mechanical behaviour of eggshell membranes under tensile loading has been studied. Samples from different bird species (hen, goose and Japanese quail) have been used. Samples were cut out of the membrane in latitudinal direction. TIRAtest 27025 tensile testing machine equipped with a 200 N load-cell was used. Tensile deformation exhibits both non-linear as well as linear region. The experiments were performed at five loading velocities 1, 10, 100, 400 and 800 mm.min−1. The main parameters describing the eggshell strength increase with the loading rate. This dependence exhibits the same qualitative features as the rate dependence of the eggshell strength.