Effect Of Crosshead Speed Research Articles

Effect of Crosshead Speed and Volume Ratio on Compressive Mechanical Properties of Mono- and Double-Gyroid Structures Made of Inconel 718.

The current development of additive technologies brings not only new possibilities but also new challenges. One of them is the use of regular cellular materials in various components and constructions so that they fully utilize the potential of porous structures and their advantages related to weight reduction and material-saving while maintaining the required safety and operational reliability of devices containing such components. It is therefore very important to know the properties of such materials and their behavior under different types of loads. The article deals with the investigation of the mechanical properties of porous structures made by the Direct Metal Laser Sintering (DMLS) of Inconel 718. Two types of basic cell topology, mono-structure Gyroid (G) and double-structure Gyroid + Gyroid (GG), with material volume ratios of 10, 15 and 20 %, were studied within our research to compare their properties under quasi-static compressive loading. The testing procedure was performed at ambient temperature with a servo-hydraulic testing machine at three different crosshead testing speeds. The recorded data were processed, while the stress-strain curves were plotted, and Young's modulus, the yield strength Re0.2, and the stress at the first peak of the local maximum σLocMax were identified. The results showed the best behavior under compression load among the studied structures displayed by mono-structure Gyroid at 10 %. At the same time, it can be concluded that the wall thickness of the structure plays an important role in the compressive properties but on the other hand, crosshead speed doesn´t influence results significantly.

Effect of cross-head speed and temperature on the mechanical properties of polypropylene and glass fiber reinforced polypropylene pipes

Recently, glass fiber reinforced polypropylene is commonly used in scientific and industrial applications such as marine, aerospace, automotive, and construction industries among other materials because of their low cost, lightweight, easy processing, and high reliability. For those promising characteristics, researches have been undertaken for understanding the thermal and mechanical behaviors of polypropylene. The main objective of this study is to investigate the mechanical properties of polypropylene (PP) and glass fiber reinforced polypropylene (GFPP) pipes, which are used in water distribution networks and compressed air systems. Tensile tests were performed at different cross-head speeds at room temperature while, flexural tests were conducted at different cross-head speeds with five distinct temperatures 23, 35, 50, 70, and 90 °C. The experimental results show that both materials are sensitive to cross-head speed, temperature, and holding time. Additionally, the percentage of elongation at break and toughness of GFPP are lower than that of PP. However, the elastic modulus and yield stress of GFPP are higher than that of PP at the same cross-head speed. On the other hand, the bending energy and the dissipated energy of GFPP are higher than that of PP under all cross-head speeds and testing temperatures. PP gains 20.4% and GFPP gains 15.2% bending energy with raising cross-head speed from 5 to 50 mm/min. Also, a decrease in flexural modulus for both materials occurs with raising temperature from 23 to 50 °C.

Fracture Behavior of Cracked Ring Specimen at Different Crack Positions

Abstract The previous research review of piping systems revealed that the plastic pipe companies suffered from many problems in natural gas pipeline systems. One of the most significant problems that appeared in the piping systems are external cracks due to manufacturing processes, welding technique, and installation processes. The principal goal of the present experimental study is to predict the crack growth behavior and energy release rate of cracked ring specimens made from high-density polyethylene (HDPE) under different crack position angles and various crosshead speeds. The effect of loading rate on the external radial crack at different crack position angles plays an important role in the prediction of fracture behavior of plastic pipe materials. For this reason, it is necessary to conduct a study for the fracture analysis of pipe ring specimens under tension loading with double external cracks at constant radial crack length to width ratio equal a/W = 0.5. A precracking machine is designed especially in the present experimental study to simulate the actual radial cracks at outer surface of pipe ring specimens. The effects of crosshead speed and crack position angle revealed a significant effect on the energy release rate and maximum applied load under tensile load.

The impact of crosshead speed on the strength of spruce wood (Picea abies L.)

The effect of crosshead speed on the strength of spruce wood (Picea abies L.). This work examines the compression and tensile strength along the grain and bending perpendicularly to the grain of spruce wood was investigated at various crosshead speeds. The dependence of the immediate strength on the crosshead speed takes the form of an exponential function for compression and tension along the grain and bending perpendicular to the grain. The study showed that as the crosshead speed increases, the ultimate strength value increases regardless of the type of stress occurring. The bending strength is between the compression and tensile strength values. The strength for compression along the grain for the spruce wood tested is 50% of strength tension along grain length and 57% of the bending strength. The bending strength corresponds to 88% of the tensile strength.

Robust formulation for the design of tissue engineering scaffolds: A comprehensive study on structural anisotropy, viscoelasticity and degradation of 3D scaffolds fabricated with customized desktop robot based rapid prototyping (DRBRP) system

This study investigates the scaffolds' structural anisotropy (i.e. the effect of loading direction), viscoelasticity (i.e. the effect of cross head speed or strain rate), and the influence of simulated physiological environment (PBS solution at 37°C) on the mechanical properties. Besides, the in vitro degradation study has also been performed that evaluates the effect of variation in material and lay-down pattern on the scaffolds' degradation kinetics in terms of mass loss, and change in morphological and mechanical properties. Porous three dimensional (3D) scaffolds of polycarprolactone (PCL) and polycarprolactone-polyethylene glycol (PCL-PEG) were developed by laying down the microfilaments directionally layer-by-layer using an in-house built computer-controlled extrusion and deposition process, called desktop robot based rapid prototyping (DRBRP) system. The loading direction, strain rate and physiological environment directly influenced the mechanical properties of the scaffolds. In vitro degradation study demonstrated that both PCL and PCL-PEG scaffolds realized homogeneous hydrolytic degradation via surface erosion resulting in a consistent and predictable mass loss. The linear mass loss caused uniform and linear increase in porosity that accordingly led to the decrease in mechanical properties. The synthetic polymer had the potential to modulate hydrophilicity and/or degradability and consequently, the biomechanical properties of the scaffolds by varying the polymer constituents.

Effects of Crosshead Speed on the Quasi-Static Stress–Strain Relationship of Polyethylene Pipes

Quasi-static stress–strain relationship of polyethylene (PE) pressure pipe that plays an important role on its long-term performance has been established by removing the viscous stress component from the experimentally measured total stress. Work reported here is focused on the influence of crosshead speed on the notched pipe ring (NPR) specimens that are prepared from PE pressure pipe of 2 in. in diameter. Viscous component of the stress–strain relationship was determined using a spring–damper–plastic element model, calibrated using results from stress relaxation tests. Crosshead speeds considered for the initial stretch of the stress relaxation tests are 0.01, 1, and 10 mm/min which due to the relatively uniform deformation in the gauge section generate the same order of difference in the strain rates. Results from the study suggest that the quasi-static stress–strain relationship is affected by the crosshead speed used to generate the deformation, and the trend of change is opposite to the total stress counterpart that includes the viscous component.

Formation of deformation band in 5083-O aluminum alloy sheet tensile-deformed at 318 K

It is well known that plastic deformation results in formation of deformation bands for some aluminum alloy sheets. However, there are few reports dealing with the formation characteristics of deformation bands, such as a position and an order of deformation bands. 5083-O aluminum alloy sheet was tensile deformed in order to investigate in detail the formation characteristics of deformation bands. The tensile test was carried out at 318 K and the effects of cross head speed on the formation characteristics were also examined. Many of second deformation band were formed to the first one in the partially overlapping shape, and a similar tendency was ascertained about the deformation band afterwards. Since the deformation bands formed in the early stage had a tendency to generate in the order, the formation behavior of deformation bands was possible to classify into two patterns. The ordering formation of deformation bands was affected by both an interruption period of tensile test and a geometrical shape of previously formed deformation bands. It is thought that microstructure changes due to atomic diffusion brought the variation of ordering formation of deformation bands. The amplitude of a load fluctuation in the load versus displacement curves was changed depending on the position where the deformation band was formed.

The effect of crosshead speed on the joint strength between Sn-Zn-Bi lead-free solders and Cu substrate

The solder joints between Cu/Sn-40Pb/Cu lead solder and Cu/Sn-9Zn/Cu and Cu/Sn-8Zn-3Bi/Cu lead-free solders were studied. The study focuses upon the formation of interface intermetallic (IMC), adhesive strength of the joints and the fracture morphology of the as-soldered soldered joints. For Sn-40Pb, Cu 6Sn 5 IMC was formed. For Sn-9Zn and Sn-8Zn-3Bi solders, two layers were detected. For Sn-9Zn solder, the first layer next to the solder is a Cu 6Sn 5 phase with some Zn dissolve in it. The second layer next to the Cu substrate is γ-Cu 5Zn 8 phase. While for Sn-8Zn-3Bi solder, the first layer is mixture of Cu-Sn + Cu-Zn phase and the second layer is γ-Cu 5Zn 8 phase. Sn-8Zn-3Bi solder has the highest strength followed by Sn-40Pb and Sn-9Zn, respectively, and their strength increases with crosshead speed. The fracture of the solder joints occurs in the elastic strain region or after a small plastic strain with Sn-40Pb solder has the highest strain followed by Sn-8Zn-3Bi and Sn-9Zn solders. The fracture surface of the three solders investigated showed ductile dimple appearance. The addition of 3% Bi increases the tensile strength and ductility of the Sn-Zn-Bi system.

Influence of branch content, comonomer type, and crosshead speed on the mechanical properties of metallocene linear low‐density polyethylenes

AbstractThe effects of branch content (BC) and comonomer type on the mechanical properties of metallocene linear low‐density polyethylene (m‐LLDPEs) were studied by means of a stress–strain experiment at room temperature. A total of 16 samples with different BCs and comonomer types were used. In addition, the effect of crosshead speed on the mechanical properties of m‐LLDPEs with different BCs was examined. The degree of crystallinity (Xt) of these copolymers was determined by differential scanning calorimetry. In addition, Ziegler–Natta linear low‐density polyethylenes (ZN‐LLDPEs) were also studied for comparison purposes. The increase in BC of m‐LLDPEs decreased Xt and the modulus. However, the ZN‐LLDPEs showed higher small‐strain properties but lower ultimate properties than the m‐LLDPEs with similar weight‐average molecular weights and BCs. In comparison with low‐BC resins, m‐LLDPEs with high BCs exhibited a stronger strain hardening during the stress–strain experiments. Strain hardening was modeled by a modified Avrami equation, and the order of the mechanically induced crystal growth was in the range of 1–2, which suggested athermal nucleation. The crosshead speed was varied in the range 10–500 mm/min. For low‐BC m‐LLDPEs, there existed a narrow crosshead speed window within which the maxima in modulus and ultimate properties were observed. The location of the maxima were independent of BC. The effect of the crosshead speed on the mechanical properties of the m‐LLDPEs was a strong function of BC. However, highly branched m‐LLDPE in this experiment showed a weak dependence on the crosshead speed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 5019–5033, 2006

The influence of matrix chemical structure on the mode I and II interlaminar fracture toughness of glass‐fiber/epoxy composites

AbstractThe present paper is concerned with Mode I and Mode II delamination tests performed on three different glass fiber reinforced epoxy composites, chosen to obtain different final structures. The effect of crosshead speed on the fracture resistance of the composites was also analyzed. It was found that Mode I propagation values (GIC) increase as the crosshead speed decreases, probably because of the increase of brittleness in the studied range. An Arrhenius type relation between GIC and the glass transition temperature of the epoxy resin/amine system (Tg) was found. Mode II initiation values (GIICinit) and apparent shear strength (SH) were found to increase with the decrease of Tg. The relation between matrix toughness and composite interlaminar fracture toughness was also considered. Finally, the GIC propagation values were compared to the data available in literature for similar materials.

Cracking Behavior of Fused Silica Glass in Sphere Indentation

The present paper describes cracking behavior of brittle materials in sphere indentation experiment. Fused silica glass plates were used for the specimen. An electro-mechanical testing apparatus was applied for the experiment. A silicon nitride sphere was penetrated with various cross head speed in air at room temperature. Au coating was applied on the testing surface to avoid the effect of corrosion. The cracking behavior was observed continuously during the test by installing a CCD camera with a lens assembly behind the specimen and was recorded with a digital memory. Acoustic emission (AE) measurement was also connected for the evaluation. The indentation strength based on an elastic contact theory was calculated. Reliability of the fracture load determination by AE measurement and the effect of cross head speed on the cracking behavior were evaluated. Obtained results revealed that the control of cross head speed was important for the indentation strength measurement.

Effect of crosshead speed on the fracture toughness of soda-lime glass, Al2O3 and Si3N4 ceramics determined by the surface crack in flexure (SCF) method

The fracture toughness of soda-lime glass, Al2O3 and Si3N4 specimens was measured by the surface crack in flexure method. For the soda-lime glass specimens, the fracture toughness was calculated from the initial crack size and flexure strength, and the value increased with increasing crosshead speed. This trend seems to be related to the difficulty in determining the critical crack size at fracture, since slow crack growth occurs during bending test. For the Al2O3 specimens, a halo region (stable crack growth region) was formed around the initial precrack during bending test. The halo size increased and the resultant flexure strength decreased with decreasing in the crosshead speed. The halo region, however, could not be observed in the Si3N4 specimens. Despite of the difference in the appearance of halo region, the fracture toughness of the Al2O3 and Si3N4 specimens was constant irrespective of the crosshead speed when the values were calculated with the critical crack sizes at fracture (halo incorporated crack sizes). The constant fracture toughness with the crosshead speed could be explained by the relation between the changes of halo size (thus critical crack size at fracture) and resultant flexure strength.

Crack growth behavior in a solid propellant

The local behavior near the crack tip and the crack growth behavior in a composite solid propellant containing hard particles in a rubbery matrix, under various loading conditions, are investigated. In this study, three temperatures (165°F, 72°F and −65°F) and two crosshead speeds (2.54 mm/min and 12.7 mm/min) are considered. Experimental results reveal that the local behavior (blunting, voiding, coalescing and growing) are the same, differing only in a quantitative sense. Crack growth occurs through a blunt-growth-blunt-growth mechanism of extension which is highly nonlinear. Experimental results also reveal that the effect of crosshead speed on crack behavior is considered small relative to that of temperature.

Local Fracture and Crack Growth Behavior in a Particulate Composite Material

In this study, centrally cracked sheet specimens made from polybutadiene rubber embedded with hard particles were used in crack propagation tests. The precracked specimens were tested at two constant crosshead speeds, 0.58 mm/min and 50.8 mm/min, at room temperature. The effect of crosshead speed on the local fracture and the crack behaviors were investigated and the results are discussed.

Dentin bonding system. Part II: effect of crosshead speed

Dentin bond strengths are normally evaluated by conducting mechanical tests in tensile and/or shear mode at a certain level of crosshead speed. According to the literature review, crosshead speed is varied in a relatively wide range from 0.1 mm/min to 10.0 mm/min (with the exception of a few studies conducted above 10.0 mm/min). It was also found that crosshead speeds of 0.5, 1.0, 2.0 and 5.0 mm/min were commonly employed to evaluate dentin bond strengths for both tensile and shear modes, although no rationale for selecting the crosshead speed was described in the articles. For testing dentin bond strengths, no plastic deformation should be involved, and fracture only should take place during the fracturing process. With the Scotchbond Multiple-Purpose/Z100 bonding system, tensile bond strengths were evaluated at crosshead speeds of 0.1, 0.5, 1.0, 5.0 and 10.0 mm/min. It was found that (i) there was no strain rate sensitivity when the test was conducted below the 1.0 mm/min crosshead speed, and (ii) if the crosshead speed exceeded 1.0 mm/min, a strain rate dependency of the tensile bond strengths was observed. Knowledge that the composite resin (Z100) did not exhibit strain rate dependency influenced the conclusion that (iii) the above observed strain rate dependency was solely due to the mechanical response from the bonding interface region.

Stress‐strain behavior and dynamic mechanical properties of poly(1,1‐dimethyl‐1‐sila‐cis‐pent‐3‐ene), poly(1‐methyl‐1‐phenyl‐1‐sila‐cis‐pent‐3‐ene) and of these polymers after crosslinking with sulfur

AbstractMechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1‐dimethyl‐1‐sila‐cis‐pent‐3‐ene) (I) and poly(1‐methyl‐1‐phenyl‐1‐sila‐cis‐pent‐3‐ene) (II). Tensile strength, elongation at break, modulus, bending modulus, Tg, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.

An Experimental Study of the Loading Rate Effect on the Crack Growth Behavior in a Composite Solid Propellant

The crack growth behavior in a highly filled composite solid propellant was studied through the use of a centrally cracked strip biaxial specimen. The specimen was tested under a constant crosshead speed at room temperature. In this study, three dif ferent crosshead speeds and two different crack lengths were considered. During the ex periment, a video camera was used to monitor the crack growth and a tape-recorder was used to record the load as a function of time. The raw experimental data (crack length, load, time) together with a response surface equation (relating the normalized stress inten sity factor to the two half crack lengths) were used to calculate the instantaneous crack growth rate and the associated stress intensity factor. The experimental data were analyzed to investigate the effect of crosshead speed on the crack growth behavior in the material. In addition, the local fracture behavior near the crack tip was also investigated and the results were discussed.

The effects of crosshead speed and temperature on the stress corrosion cracking of Cu-30% Zn alloy in ammoniacal solution

Stress corrosion cracking (s.c.c. of Cu-30% Zn alloy in Mattsson's solution (0.05 mol/l CuSO 4 + 0.5 mol/l (NH 4) 2SO 4, pH 7.2) was investigated as a function of temperature (298 K–323 K) and crosshead speed (10 −5 mm/min to 1 mm/min). Crack propagation behaviour in a crosshead speed of 10 −4 mm/min at 298 K was also studied. All tests were carried out using a slow strain rate technique. Cracks occurred intergranularly under all experimental conditions used. At high crosshead speeds (5 × 10 −3 mm/min to 1 mm/min) the susceptibility to s.c.c. increased with increasing temperature. At slow crosshead speeds, however, an inverse effect of temperature on the susceptibility was revealed. Constant crack velocities were obtained in both specimens with or without surface coating, and the velocity in the coated specimen was lower than that in the uncoated specimen by one order of magnitude. Scanning electron microscopic examination revealed that ahead of intergranular cracks small corrosion pits were formed along grain boundaries. Based on the above experimental results, the mechanism of intergranular s.c.c. of Cu-30%Zn alloy was discussed by considering the growth rate of microcrack formed along grain boundary and the corrosion rate (or repassivation rate) of the microcrack.

Computer Simulation of the Tension Test: Effect of Testing Conditions

Abstract Tension tests performed at constant crosshead speed have been simulated in a computer, and stress-strain, load-displacement, and strain rate-strain curves in uniform deformation under various testing conditions were obtained. Hart's phenomenological description of the plastic deformation was used together with a simple form for the stress and strain rate dependence of the material parameters that appear in this description. Various materials were simulated and the effects of crosshead speed, initial “hardness” state, specimen dimensions, and machine stiffness were studied in each case. The implications of these results in the specification and interpretation of tension tests are discussed. Particular attention is given to the relation between the onset of plastic instability and the point of maximum load in the tension test.

SPECIFIC GRAVITY DETERMINATION WITH A UNIVERSAL TESTING MACHINE

SUMMARY —A rapid, precise technique for determining specific gravity of fruits and vegetables was developed. The method utilized a universal testing machine. The effects of crosshead speed, choice of standard density fluid and weight measurements were studied and optimized. A standard sphere of known volume and weight was used to compare this method with other techniques now used. In addition to using the standard sphere, tomatoes were studied to evaluate the efficiency of this method. Calculation of specific gravity involved determining fruit volume and weight. Other volume measurement techniques investigated proved inaccurate or too time‐consuming. An Instron universal testing machine was used in measuring the buoyancy force of a fruit submerged in a standard density fluid. The buoyancy force is directly related to the fruit volume. Error analysis showed relatively low sensitivity to errors in weight measurement, but was influenced mainly by errors in determining the fluid density. This error was minimized by use of high‐density fluids; thus, saturated salt brines and high‐density organic fluids were used for the experimental work.