Specific Shear Energy Research Articles

Study on the Shear and Bending Mechanical Properties of Millet Stem

To determine the patterns and influencing factors of the mechanical properties of millet stems from different varieties during the maturity period, this study employed a complete block experiment method and conducted shearing and bending tests on millet stems using the INSTRON5544 electronic universal material testing machine. The research investigated the variation in the shear strength, specific shear energy, bending strength, elastic modulus, and bending stiffness at different internode positions of the stems of Changza 466, Zhangza 16, and Jingu 21 during their maturity period. The results indicated that the variety had a significant impact on the mechanical properties of millet stems: from largest to smallest, the order of shear and bending forces was Jingu 21, Zhangza 16, and Changza 466. The shear strength and bending strength of Jingu 21 were the greatest among the three stem samples. The internode position significantly affected the shear mechanical properties of the millet stems, showing a general trend of decreasing shear strength with ascending internode position. The effect of the internode position on the bending stiffness was highly significant, whereas its impact on the bending strength and elastic modulus was not significant. The shear strength of the millet stems ranged from 3.866 ± 1.086 to 6.953 ± 2.208 MPa, significantly lower than the bending strength, which ranged from 18.934 ± 4.374 to 34.286 ± 6.875 MPa. The lowest shear strength and specific shearing energy, recorded at the fifth internode, were 4.028 ± 1.918 MPa and 15.097 ± 12.633 MJ/mm2, respectively. Jingu 21 and Changza 466 exhibit better lodging resistance than Zhangza 16. It is recommended to use a cutting-type platform for harvesting millet stems, with the cutting height set at the fifth internode position. This study provides a theoretical basis for the design of millet harvesting machinery and the selection of harvest parameters.

Effects of Cutting Parameters on the Shearing Properties of Oilseed Rape (Brassica Napus L.) Shoots in Harvesting

Highlights Cutting parameters affect the shearing properties of ultimate shear stress and specific shear energy of oilseed rape shoots harvesting. The oilseed rape shoots harvester blade was optimized using a central composite design (CCD) experimental test. The interaction term of blade thickness and oblique angle significantly affect the ultimate shear force and specific shear energy. Provide a reference for designing oilseed rape shoots harvesting machinery. Abstract. Oilseed rape (Brassica napus L.) shoots are used as an edible nutritious and healthy vegetable. However, there is little information for the effects on cutting parameters on the oilseed rape stalk shearing properties to harvest fresh shoots. This study used the single factor method and response surface methodology (RSM) along with central composite design (CCD) to examine the effects of the blade operating and structural parameters, such as the blade loading velocity, the bevel angle, the oblique angle, and the thickness, on the response variables of ultimate shear stress and specific shear energy. The RSM analysis results demonstrated that the interaction term of blade oblique angle and thickness affect the response variables. Optimized operating and geometry parameters for minimizing response variable values were 195 mm min-1 for loading velocity, 16.4° for bevel angle, 16.3° for oblique angle, and 3.2 mm for thickness. Moreover, under these optimal parameters, the ultimate shear stress and specific shear energy were reduced by 31.37% and 40.95%, respectively, compared to the cutting parameters of the prototype harvester. This study concluded that the appropriate cutting parameters could effectively decrease the shear force and energy requirements, which provided a vital basis for designing and developing the cutting device for the oilseed rape shoots harvester. Keywords: Cutting parameters, Oilseed rape shoots, Shearing experimental test, Specific shear energy, Ultimate shear stress.

Microstructure and micromechanical properties evolution pattern of metamorphic layer subjected to turning process of carbon steel

Turning process results in microstructure alteration and forms a metamorphic layer beneath the machined surface, which influence micromechanical properties. The metamorphic layer induced by turning was divided into severe deformation layer (SDL) and moderate deformation layer (MDL) through grain size distribution, and the microstructure was observed and characterized by electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The model to predict the depth of SDL (hSDL) based on dynamic recrystallization and specific shear energy (US) in the cutting process was established, and the results showed that ΔUS had a linear relationship with hSDL (R2 = 0.8799). The micromechanical properties of SDL, MDL, and bulk material were characterized by micro-hardness and micropillar compression tests. The increment of micro-hardness in SDL (increased by 66.4 % on the bulk material) is mainly due to the Hall-Petch effect caused by nanocrystals formed through dynamic recrystallization, and the micro-hardness in MDL (increased by 24.1 % on the bulk material) is affected by the superposition of the Hall-Petch effect and Taylor strengthening caused by the gradient distribution of grain size and dislocation density. The yield stress (σy) obtained from the micropillar compression test decreased successively in SDL, MDL, and bulk material (from 1072 MPa to 604 MPa). The influence mechanism of the critical resolved shear stress (τCRSS) and Schmidt factor (SF) on SDL, MDL, and bulk material were illustrated.

Machined surface defects monitoring through VMD of acoustic emission signals

Machined surface defects influence functional properties of the component, such as reducing carrying capacity and shortening fatigue life. This study collected the cutting force and the acoustic emission (AE) signals, analyzed the effect of shear and ploughing effect on the frequency of the AE signals in machining, built the relationship between the first-order mode components (IMF1) and the second-order mode components (IMF2) of AE signals and the shearing and ploughing process respectively through variational mode decomposition (VMD). A new parameter Er = (RMS2/RMS1)2 was proposed as the signal feature to monitor machined surface defects, which represented the ratio of specific ploughing energy and specific shear energy. The results showed that when Er was in the range of 0.03–0.05, the machined surface quality was good, once it was higher than 0.05, the ploughing effect between the flank face and the machined surface was severe, thereby causing machining-induced surface defects.

Optimisation and numerical simulation of shearing blade used for citrus seedling grafting

Manual grafting for citrus seedlings is still the most common grafting technique, which is a labour-intensive and time-consuming procedure. This study investigated the effect of blade geometry and operating parameters, including bevel angle, slide cutting angle, blade thickness, and loading rate on the shear quality, shear force and shear energy of citrus rootstock seedlings. Box-Behnken design was employed to conduct experiments and explore the interaction effect of selected factors on indicators. The optimal structure and operating parameters were determined to be 285 mm min −1 for loading rate, 27° for bevel angle, 50° for slide cutting angle, and 2.83 mm for blade thickness. Under these conditions, the predicted values of the evaluation indices were determined to be 66.70% for percentage of smooth shear without splitting failure, 747.98 N for average value of the maximum shear force and 55.48 mJ mm −2 for specific shear energy. Based on the optimal parameters, with the help of reverse modelling method, a numerical simulation model was established to simulate the shearing process and analyse the stress distribution in the stalk and blade. The maximum effective stresses of the rootstock specimen and blade in the shearing process were about 28.11 and 229.82 MPa, respectively. This study indicates that optimisation of operational parameters of shearing blade will result in improving shear quality and saving significant energy. The results are beneficial to practical applications in design and development of shearing device for future citrus grafting robots. • Shearing blade of citrus rootstock was optimised by using Box-Behnken design. • Quantifying damage level of citrus rootstocks to evaluate shear quality of blade. • Establishing rootstock shearing model by using reverse modelling method. • Stress distribution in rootstock and blade were predicted through co-simulation.

Effects of blades types on shear force and energy requirement of paddy stem

This study was aimed to determine of the shearing force and shearing energy of paddy stem as a function of blade type, blade-edge angle and cutting speed. The Karacadag white paddy variety was used as plant materials. Shearing properties were measured by a universal testing machine. Depend on measured shear force and cross-section area of paddy stem, energy values were calculated by measuring the surface area under the cutting force-deformation curve for each test separately. The tests were conducted at five blade angles, five loading speed with various three different type blades. The tests results showed that the shearing force, shearing strength, shearing energy, specific shearing energy and extension at maximum load were affected significant (p<0.01) by blade type, cutting angle and cutting speed. While the lowest values were determined at serrated 2 blade types, followed by the serrated 1 and flat-edge blade. The paddy stalk shearing force and energy values has increased with decrease in the blade edge angle from 90° to 50°. The highest force and energy values were measured at 90° cutting edge of blade as 25.47 N and 5.8 N cm. The effect of loading speed on the cutting forces, cutting strength, cutting energy and specific cutting energy were found significant (p<0.01). The shearing and energy has slightly decreased with an increase of blade cutting speed. While the highest values were found at 2 m s-1 loading speeds, the lowest values were found at 6 mm s-1 cutting speed.

Investigation of the specific cutting energy and its effect in shearing dominant precision micro cutting

Abstract The analysis of SCE (specific cutting energy) is vital for determining the machining efficiency. Conventionally, the machining forces are used to determine SCE, which is quantified as the energy that is consumed to remove unit volume of material. To correlate the micro-mechanics of material deformation and small-scale material removal in machining, in this research paper, the SCE has been modelled with consideration of shearing mechanism. While developing the model, small scale material indentation and deformation phenomena have been correlated with complex tool-work interaction behaviour in micro machining. The experiment was conducted for validation of the model for different light-weight materials i.e. Al alloy and Cu alloy. The investigation was done through the analysis of cutting forces and the visual examination of microchip morphology. It was found that the nonlinear increase and sharp fall of specific shearing energy (UShe) occur owing to the variations of the material removal mechanism. This is especially valid for lower values of UCT (undeformed chip thickness).

Effects of Moisture Content and Knife Bevel Angle on Shearing Properties of Cassava Stems

The effects of the moisture content and the knife bevel angles on the shearing properties of cassava stem were examined. In order to determine their effects on the shearing stress and shearing energy of cassava stems, the stems were classified into three regions: the lower, middle, and the upper regions. The results showed that the shearing stress and the specific shearing energy had increased as the knife bevel angle was increased from 20 to 40 degrees and that the moisture content had decreased from 64.27 to 17.67% w.b. The maximum shearing force, shearing stress, and the specific shearing energy were found to be 2.16 kN, 4.62 Mpa, and 55.58 mJ/mm2, respectively. Due to structural heterogeneity, the shearing stress and specific shearing energy were found to be higher in the lower regions of the stems.

Effects of moisture content, internode region, and oblique angle on the mechanical properties of sainfoin stem

The effects of moisture content, internode region, and oblique angle on several mechanical properties of sainfoin stem were determined. The selected mechanical properties used were the shearing stress, specific shearing energy, bending stress, and modulus of elasticity when bending. The experiments were carried out with wet basis (WB) moisture contents of 71.76%, 45.57%, and 25.57%, at the third and second internode regions from the bottom up to the top, and 2 oblique angles (0° and 28°). The research results showed that the shearing stress of sainfoin stem increased as the moisture content increased, but decreased towards the upper internode of the stem. With the same moisture content, the shearing stress values obtained at an oblique angle of 28° were lower than those at an oblique angle of 0°. The maximum shearing stress and specific shearing energy were 5.76 MPa and 16.65 mJ mm-2 with a WB moisture content of 71.76% and an oblique angle of 0° at the first internode, respectively. The bending stress increased with decreasing moisture content. The maximum bending stress was 36.45 MPa for the lower region with a WB moisture content of 25.57% and the modulus of elasticity when bending decreased with an increase in the moisture content, and it was towards the upper region. The average modulus of elasticity values varied between 1.60 and 0.64 GPa.

Mechanical properties of cotton shoots for topping

Cutting the shoots of cotton plants (topping) at about 10–20 cm from the top of plants is a cultural practice, which may offer advantages to improve yield and yield components in cotton production. The cutting forces of plant stalks were reported in the literature, which help understand the mechanical properties of stalks for a cultivar of field crops. However, the shearing characteristics of cotton shoots have not been addressed yet. The objective of this study was to determine some physical and mechanical properties of cotton (Gossypium hirsutum L.) shoots. The test specimens were obtained from two different plant segments, i.e. 0–15 cm (Segment A) and 16–30 cm (Segment B) from the top of cotton plants, in 21 plots in an ongoing cotton topping study. The samples were collected from each plot and were subjected to shearing test using a universal test machine in the laboratory. In Segment A, average shoot diameter, shearing force, water content, maximum shearing stress, and specific shearing energy were determined to be 4.35 mm, 73 N, 72%, 4.94 MPa, and 0.069 J mm−2, respectively. In Segment B the same parameters were 5.79 mm, 121 N, 64.8%, 4.65 MPa, and 0.078 J mm−2, respectively. The difference between the Segment A and B was significant at 5% level for shearing stress while all others parameters showed differences at 1% level. Although displacement at the bioyield point was similar in both sampling locations, the maximum shearing force requirement was more (121 N) in Segment B compared with Segment A (73 N) suggesting that topping should be done as high as possible from the ground to complete the topping process with low energy consumption. In terms of cutting energy requirement, it was concluded that the topping should be done as early as possible from 100 to 120 days from the planting.

An experimental investigation of micro-milling brass considering run out by carbide micro-end mills

This paper presented the effect of run out on the experimental characteristic of micro-milling brass using carbide micro-end mills. A method of calculation and measurement for the run out of tool-holder-spindle assembly in micro-end mill was developed. A series of micro-milling process experiments were carried out under varying cutting parameters. The effect of run out on cutting forces, effect of cutting parameters on surface roughness, and size effect were analyzed. It was seen that the cutting force signature was seriously affected by run out in the micro-milling process. When the feed per tooth is less than the run out, the cutting force signals showed that only one cutter flute engaged in cutting process due to the effect of run out. It was also seen that the cutting force signature showed erratic variations due to the effect of tool–workpiece and the run out of tool tip at higher spindle speed. Surface roughness was affected by both cutting speed and feed per tooth. For lower cutting speed, there was increase in the surface roughness with the decrease in the cutting speed due to the effect of built-up edge. For higher cutting speed, there was increase in the surface roughness with the increase in the cutting speed due to dominance of the shearing effects. When the feed per tooth was less than the minimum chip thickness, due to the indentation and ploughing-dominated process, nonlinear increase of specific shear energy can be obtained. At lower feed per tooth, the specific energy increases with increased cutting speed. These results are used to provide strategies to optimize cutting parameters and achieve better surface quality in micro-milling brass process.

An Experimental Investigation of Cutting Forces in Micro End-Milling Process

This paper presents an experimental study of cutting forces during micro end-milling of brass. The influences of cutting speed and feed per tooth on cutting forces have been researched. The results show that the resultant force Fr and feed force Fx significantly increase with increasing the feed per tooth. The resultant force Fr, feed force Fxand normal force Fy increase with increasing cutting speed. The specific shear energy is also investigated. It is observed that the specific shear energy increases greatly with decreasing the feed per tooth when the feed per tooth is less than minimum chip thickness.

Specific energy based evaluation of machining efficiency

Rubbing and ploughing increase the tool tip energy demand in machining. An efficient set of cutting conditions would direct the energy into material shearing and hence selecting the efficient set is a value adding activity. In this work, a side milling tests were conducted on a milling machine tool to investigate the specific ploughing energy on AISI 1045 steel alloy, titanium 6Al–4V alloy and aluminium AW6082-T6 alloy materials. The relationship between the cutter swept angle and the specific ploughing energy is explored. An optimised model for width of cut and undeformed chip thickness at which ploughing effect would be minimal is proposed. The proposed methodology can be used to evaluate machining efficiency based on maximum specific shear energy and also to derive the specific ploughing energy for minimum tip energy demand.

Mechanical Properties of Sugarcane Stalk

The study was undertaken to assess the mechanical properties including compressive and shearing strength of sugarcane (Saccharum officinarum L.) stalks for four varieties viz., Co99004,CoC-671,Co-85004 and Co-86032. The highest value of compressive strength (47.75 kN) at lower section was recorded for the variety Co-86032, whereas the lowest value (34 kN) was obtained with Co-85004. The maximum value of compressive strength for top section (49.25 kN) was recorded with CoC-671 and the minimum (39.75 kN) for the variety Co-99004. The cutting force required for shearing sugarcane stalk, ultimate cutting stress and specific shearing energy were determined at two sections for all the four varieties. It was observed that the maximum value of shearing force (1333.89 N) would be observed for the variety Co85004 at lower section and it was (815.29 N) recorded for the variety CoC-671.The maximum value of ultimate cutting stress was (1.98 MPa) with Co-85004 at the lower section, while it was minimum (1.05 MPa) for the variety Co-99004. Similarly, the maximum value of specific shearing energy (39.68 mJ/mm2 ) was recorded for the variety Co-85004 for the lower section, while it was minimum (13.06 mJ/mm2 ) with CoC-671.

Mechanical Shear and Tensile Properties of Selected Biomass Stems

<abstract> <bold><sc>Abstract. </sc></bold>Perennial grasses and corn stalks can supply abundant lignocellulosic feedstock in the northern Great Plains of the U.S. There is a need to understand the mechanical properties of these crops for better handling and processing of biomass feedstocks in bioprocessing industries. The objectives of this research included determination of tensile and shear stresses of big bluestem, corn stalk, intermediate wheatgrass, and switchgrass stems and measurement of specific tensile and shear energies during tensile and shear failure. A high-capacity MTI-100K universal testing machine equipped with adapted tensile clamps and a specially designed and fabricated double-shear device were used for tensile and shear testing. Ultimate shear stresses were not statistically different for big bluestem, corn stalk, and intermediate wheatgrass, with values of 7.33, 8.53 and 6.23 MPa, respectively, which were less than switchgrass at 13.39 MPa (p < 0.05). Corn stalk had the greatest ultimate tensile stress of 69.30 MPa, followed by switchgrass, big bluestem, and intermediate wheatgrass. The ultimate tensile stress and shear stress were statistically different (p < 0.05) from each other for all four feedstocks. Both ultimate shear energy and specific shear energy for corn stalk were statistically different (p < 0.05) from big bluestem, intermediate wheatgrass, and switchgrass. The evaluated shear to tensile stress ratios, expressed as percentages, were 29.3%, 12.3%, 30.5%, and 31.9%, whereas the shear to tensile energy ratios were greater, with values of 42.2%, 67.2%, 61.2%, 50.4% for big bluestem, corn stalk, intermediate wheatgrass, and switchgrass, respectively. Based on these results, shear-dominant size-reduction devices (e.g., knife mills and chippers) should be more energy efficient, and this energy efficiency should be taken advantage of when designing size-reduction devices. Further research efforts are necessary to determine the effect of moisture, crop variety, and maturity stage, as these factors are known to affect the mechanical characteristics of biomass feedstocks.

Experimental Study on Specific Shear Energy in High-Speed Machining 7050-T7451

In this paper, the specific shear energy in high-speed machining 7050-T7451 from 100m/min to 3000m/min is measured and compared with the theoretical value evaluated by the method proposed by Pawade et al. (2009). The influences of cutting speed, rake angle of cutting tool, and uncut chip thickness are also investigated and discussed. Results show that the specific shear energy decreases with the increase of cutting speed, rake angle, and uncut chip thickness. The higher thermal softening makes the specific shear energy lower.

Exploring a new method to study the agglomeration of powders: Application to nanopowders

The increasing use of nanoparticles in the production of nanomaterials has led to the identification of nanoparticle agglomeration in air or in a given medium as a key problem, both on the standpoint of process performance (i.e. product homogeneity) and above all on inhalation risks. This paper suggests a new method to evaluate the structure and the dynamics of agglomeration of a nanopowder, based upon monitoring of the shear stress of a powder which is submitted to the mechanical solicitation of a rheometer. At low and increasing shear rates, the powder flow will evolve from a Newtonian regime (dense powder) to a Coulombic regime (slightly rheofluidized dense phase). At larger shear rates, the powder will be set in suspension, which characterizes a kinetic regime governed by particle collisions. The specific shear energy, related to the specific agglomeration energy, has been calculated for different nanopowders (carbon, aluminum, silica) and compared to non-cohesive micrometric powders (glass beads). From the measurements of shear rates and stresses at the frictional/kinetic transition, agglomerate diameters have been evaluated for carbonaceous material and for silica. Values of these agglomerates can range from 200 to 500μm and are related to their propensity to break apart. The carbonaceous materials seem to be the more difficult to deagglomerate, whereas silica nanopowder agglomerates are more easily breakable. Measures of cohesiveness (or specific agglomeration energy) can be useful for assessing the dispersibility of nanopowders and their relationships to inhalation or explosion risks.

Comparison of mechanical properties of wheat and rice straw influenced by loading rates

This study investigates the comparison of mechanical properties of wheat and rice straw such as shear strength, specific shearing energy and cutting forces. The experiments were conducted at three loading rate of 15, 20 and 25 mm min -1 and three internode positions 70 (N1), 130 (N2) and 190 (N3) mm down from the ear. Results show that by increasing the loading rate, strength of wheat and rice straw changed from 8.12 to 22.94 and 6.06 to 14.33 MPa and specific shear energy was varied from 12.10 to 18.64 and 10.40 to 16.17 mJ mm -2 , respectively. Moreover, the values of cutting forces of wheat and rice straw were within the ranges 13.23 to 19.50 and 9.40 to 16.70 N. Whereas the shear strength, specific shearing energy and cutting force were higher at higher loading rate at the third internode of both straw internode positions. The shear strength, specific shearing energy and cutting force of rice straw were significantly higher (p<0.05) than that of wheat straw. With respect to the findings of the present research study, it is concluded that with decreasing loading rate of cutting blade toward the first internode, more energy can be saved by harvesting and threshing machines.

Influence of induced shear work on the properties of polyolefine nanocomposite pipes

AbstractThe use of layered silicates is steadily growing in polymer processing due to their great potential of enhancing material properties. Depending on the particle structure (agglomerated, intercalated, or exfoliated), a significantly higher level of improvement of the material properties can be achieved. The degree of exfoliation is exceedingly linked with the residence time and shear energy induced during processing. These processing parameters themselves are depending on the type of processing technique and conditions. The influence on exfoliation rate and the needed values for processing nanocomposites are not known precisely, but would be of major interest according to an optimization of mechanical and physical properties. In this work, the effect of different processing techniques (compounding, extrusion, and injection molding) on the dispersion of the nanofiller is investigated. A specific shear energy is calculated by the induced shear energy and the residence time regarding the mass throughput for better comparison. The differences in the degree of exfoliation according to dissimilarity of the chosen processing techniques are compared via various methods such as internal pressure creep rupture test, longitudinal shrinkage, and tensile test. It is shown that the calculated values are correlating with good precision, especially for the extrusion process. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

MECHANISM OF CHIP FORMATION IN HIGH-SPEED TURNING OF INCONEL 718

The mechanism of serrated chip formation during high-speed turning of Inconel 718 using PCBN cutting tools has been investigated with the aid of scanning electron microscopy and optical microscopy. A conceptual model of chip formation has been developed knowing the chip morphology. It is followed by the analysis of chip segmentation frequency and the chip forms. Further, the chip segment forms and geometry were quantitatively characterized as a function of machining parameters and the cutting edge geometry using statistical methods. The chip morphology has been correlated with the cutting forces, specific shearing energy and the resultant roughness of the machined surfaces.