Residual Plastic Research Articles

Research on the precision loss of ball screw with short-time overload impact

Ball screw is the driving functional component most frequently used for the precision equipment. To a certain extent, the transmission accuracy of precision equipment is affected by the position error of ball screw caused by the elastic–plastic deformation between ball and raceway under the overload impact. This article aims to investigate the precision loss of ball screw considering short-time overload impact. A novel precision loss model combining the Hertzian and Thornton contact theories is established to describe the variations in the axial deformation depths. Thus, the axial precision loss can be defined as the differential value between the initial no-loading travel variations and the loading stroke variations caused by the axial plastic deformation of raceway. Meanwhile, the maximum stress and the residual plastic deformation for four couples of ball-raceway materials are analyzed. Furthermore, the relationship between the precision loss and the elastic–plastic deformation is studied by the theoretical analysis and experiments. The results show that the position and precision is affected indeed by the contact deformation. The position and precision loss of the nut relative to the screw increases with the increase in the axial load. The results can help to provide the prediction for the precision life of ball screw operating in high-load condition.

Експлуатаційні дослідження показників кутового зсуву клейової полімерної пластини корінцевої частини книжкового блоку

The purpose of the work is to study the deformation of the adhesive layer of the root portion of the book block, stitched threads, the influence of the bending angles of the polymeric adhesive plate during the exploitation of book products, which contribute to the creation of zones of variable concentration of destructive stresses of the internal structure of the plate, as well as the influence of the time of the load on these areas, that proportionally influence on the reduction of the elastic properties of the plate and the development of residual plastic deformation phenomena. The amount of deformation of individual sections of a radial adhesive polymer plate, during operational loads when using book blocks stitched together, depends not only on the elastic material properties of the adhesive composition, its isotropy, the thickness of the applied layer, but also on the angles of the plate kinks that contribute to creating variable zones concentration of destructive stresses of the internal structure. Stresses occur at the edges of the joints of the glue plate with the paper of the folds of the backs of the notebooks on the one hand, and the edging paper, on the other hand, in the form of sections of compression and tension in places of discrete kinks. The duration of the loads in these areas, in proportion to the decrease in the elastic properties of the plate and the increase in the phenomena of residual deformation. Taking into account the negative influence of discrete angular bends of rooted glue polymeric plates in any part of it and the heterogeneity of the duration of loads during the exploitation of book products lead to deformation formed during bending of the plate and promotes the accelerated transformation of processes of elastic deformation into residual processes of plastic deformation. The use of high strength and high elastic adhesive compositions, which do not have a negative effect on the stiffness and bending stability of the glued system, can minimize the disadvantages of the angular displacement, which in turn will provide a prolonged operating period and a favorable competitive appearance of book products.

Revealing hydrogen-induced delayed fracture in ferrite-containing quenching and partitioning steels

Hydrogen-induced delayed fracture (HIDF) of two ferrite-containing quenching and partitioning (QP) steels, QP980 and QP1180, has been studied by deep-drawn cup tests and slow strain rate tests (SSRT) in the present work. It is found that QP980 has better delayed fracture resistance than QP1180 due to both volume fraction and distribution of ferrite. Other factors, such as residual stress, plastic strain, retained austenite and strain-induced fresh martensite, are also carefully considered, but cannot account for the difference. In the QP steels, hydrogen-induced cracks nucleate in sensitive regions such as retained austenite or strain-induced fresh martensite, and prefer to propagate along prior austenite grain boundaries (PAGBs) and martensite packet boundaries. We also found that ferrite in QP steels can be used to blunt hydrogen-induced cracks, and interrupt the continuity of PAGBs and packet boundaries. QP980 steel has a higher volume fraction of interconnected ferrite, and discontinuous PAGBs and martensite packet boundaries, which are the main mechanisms responsible for the better HIDF resistance of QP980. Therefore, it is proposed that an appropriate volume fraction and distribution of ferrite phase should be present in QP steels for better HIDF resistance.

Consequences of deep rolling on the fatigue behavior of steel SAE 1045 at high loading amplitudes

Near surface sample volumes play an important role in terms of safety and reliability of technical components especially in the case of fatigue loading. By applying mechanical surface treatment methods such as shot peening, deep rolling or laser shock peening, near surface layers can be tailored resulting in increased fatigue strength especially in the high-cycle fatigue regime. For higher loading amplitudes, increase in fatigue strength, however, is less pronounced and even detrimental consequences of deep rolling treatments have been observed. To identify the reasons for these observations, the cyclic deformation behavior of differently deep rolled, quenched and tempered sample conditions of steel SAE 1045 under high loading amplitudes has been studied and assessed with a focus on the stability of near surface residual stresses. Based on the results, it is shown that the residual stress relaxation behavior in deep rolled material conditions is strongly affected by the cyclic yield strength of each material state and, thus, is related to cyclic plastic deformation. Furthermore, residual stress stability and plastic strain depend on the stress amplitude and are closely related to each other.

Numerical analysis of hydrogen transport into a steel after shot peening

Abstract Surface peening is a potential method of suppressing hydrogen embrittlement (HE). But experimental observations in literatures have shown that it can suppress HE of steels exposed to a mild hydrogen-containing environment, but in a severe hydrogen-containing environment it enhances HE. To explain this from the perspective of hydrogen transport and concentration, this paper gives a numerical analysis of hydrogen transport into a PSB1080 high strength steel after shot peening (SP) focusing on the combined effect of residual compressive stress and SP plastic deformation on diffusion. The diffusion model established by Oriani and Sofronis et al. is used, which considers the effect of the increase of trap sites due to plastic strain and assumes that the populations of hydrogen in trap sites and in normal lattice sites are in equilibrium. The results were related to experimental observations. In mild hydrogen-containing environment, the increase of trap sites due to SP can significantly reduce the apparent hydrogen diffusivity, thus suppress the transport and resulting hydrogen concentration level in normal lattice sites. As a result, hydrogen trapped at grain boundaries is reduced, and HE mechanism changes from HEDE to simultaneous HELP and HEDE. Intergranular fracture is suppressed thus reducing HE. And the suppression of hydrogen transport increases with increasing shot velocity, as a faster shot gives rise to more severe plastic deformation. In severe hydrogen-containing environment, SP deformation has little influence on diffusivity but significantly increases trapped hydrogen, leading to irreversible hydrogen blisters hence enhancing HE.

Bottled mineral water: classic and temporal descriptive sensory analysis associated with liking

PurposeThe purpose of this paper is to determine the classic (static) and dynamic sensory profile of different bottled mineral water samples, and to evaluate the consumer’s liking of the products.Design/methodology/approachClassic quantitative descriptive analysis (QDA) and temporal dominance of sensations (TDS) were applied to four brands of bottled mineral water and the liking of the products was evaluated by consumers.FindingsThe dissolved mineral concentration is highly correlated to the liking and influences the sensory profile of the samples in a substantial way. The higher the mineral content, the lowest is the liking. Refreshing, residual plastic taste, musty, metallic taste, medicine taste and viscosity were relevant attributes to the samples differentiation through the static evaluation, while refreshing and viscosity were dominant in the dynamic monitoring. Some information might have been lost by the nature of the TDS method, based on dominance concept. Sweet taste contributed positively and musty taste negatively to the acceptance.Originality/valueThis paper demonstrated that TDS can be used as a complementary tool to the QDA, contributing to a deeper comprehension of the differences among samples, even in products with low differences, such as bottled mineral water.

Mechanical Characteristics of Hybrid Composites with ±45° Glass and 0°/90° Stainless Steel Fibers.

Lack of energy dissipation is one of the shortcomings of conventional glass fiber reinforced composites. The addition of steel fibers to the conventional FRP composite to create a hybrid composite has been recently investigated as an option to address this limitation. The current literature is limited to composites reinforced with metal and non-metal fibers of the same alignment. In this study, hybrid and nonhybrid FRP composites of different layups, fiber content, and weave type were manufactured and subjected to hysteretic tensile loads. Woven glass fabrics in ±45° orientation were hybridized with unidirectional stainless steel fabrics in 0° and 90° orientations. This put the glass and steel layers in in-plane shear and normal stresses, respectively. The nonlinear stress–strain relationship, residual plastic strains, energy dissipation capability, and failure mechanisms of hybrid and nonhybrid composite type were compared. The hybrid composites presented improved energy dissipation, tensile strength, and stiffness when compared to nonhybrid ones. The applicability of an existing constitutive model that was originally developed for in-plane shear of conventional composites was investigated and refinements were proposed to present the hysteretic stress–strain relationship after addition of steel fibers. The refined model captured the increased plastic strain values and energy dissipation because of stainless steel fibers in the hybrid composite samples. An Armstrong–Frederick plasticity model was implemented to model the stress–strain relationship of the stainless steel composite samples.

Effects of Soil Residual Plastic Film on Soil Microbial Community Structure and Fertility

Plastic films have previously displayed tremendous potential to increase water use efficiency in farmland and the yield of cash crops; however, long-term use of plastic film in soils can influence soil physiological and biochemical characteristics and change its biota. The present study aimed to investigate the effects of residual plastic film pollution on soil microbe community structure and fertility in Xinjiang province, China. Residual plastic film-contaminated soil and non-contaminated soil in Xinjiang farmland were selected for this study. The results indicated that residual plastic film pollution changed the structure of the soil biological community by significantly decreasing and increasing the abundance of Actinomycetes and Proteobacteria, respectively; further, the pollution decreased soil organic matter and inorganic nitrogen content by downregulating microbial genes related to soil carbon and nitrogen cycles and decreasing related enzymatic activities. The present results indicated that long-term residual plastic film exposure (more than 10 years) in farmland significantly decreases soil fertility and alters the microbial community structure.

A fretting finite element investigation of a plane-strain cylindrical contact of Inconel 617/Incoloy 800H at room and high temperatures

This work presents a finite element study of a 2D plane strain fretting model of a half-cylinder in contact with a flat block under oscillatory tangential loading. The two bodies are deformable and are set to Inconel 617 and Incoloy 800H at room temperature (20 ℃) and 800 ℃. However, because the results are normalized, they can characterize a range of contact scales (micro to macro). Different coefficients of friction are used at the interface. This work finds that the edges of the contacting areas experience large von Mises stresses along with significant residual plastic strains, while pileup could also appear when the coefficients of friction are sufficiently large. In addition, junction growth is investigated, showing that the direction of the growth is in the same direction of the tangential force that the weaker material (Incoloy alloy 800H) experiences. The fretting loop (caused by the tangential force during the fretting motion) for the initial few cycles of loading is generated, and it compares well with the reported experimental results. The different extents of damage at room temperature and 800 ℃ are also compared.

Model for Elastic–Plastic Contact Between Rough Surfaces

This paper studies elastic–plastic contact between Greenwood–Williamson (GW) rough surfaces, on which there are many asperities with the same radius whose height obeys the Gaussian distribution. A new plasticity index is defined as the ratio of the standard deviation of the height of asperities on the rough surface to the single-asperity critical displacement (the transition point from the elastic to the elastic-fully plastic deformation regime), which is linearly proportional to the GW plasticity index to the power of 2. The equations for the load/area–separation relationship of rough surfaces are presented based on Wang and Wang's smooth model of singe-asperity elastic–plastic contact, which is an improvement of the Kogut–Etsion (KE) empirical model based on finite element analysis (FEA) data. The load/area–separation relationship can be described by empirical Gaussian functions. The load–area relationship of rough surfaces is approximately linear. The average pressure is only function of the new plasticity index. According to Wang and Wang's conclusion that Etsion et al. single-asperity elastic–plastic loading (EPL) index is approximately equal to the ratio of the single-asperity residual plastic contact displacement to the single-asperity total elastic–plastic contact displacement, the equations for the relationship between Kadin et al. modified plasticity index (MPI) and separation of rough surfaces are also presented. In addition, the MPI is approximately linearly proportional to the separation between rough surfaces for a given new plasticity index ranging from 5 to 30. When the new plasticity index is smaller than 5, due to the large proportion of the elastic deformation in the total deformation, the MPI slightly deviate from linearity.

Damage mechanics-based approach to studying effects of overload on fatigue life of notched specimens

A continuum damage mechanics-based method is adopted to predict the fatigue life of notched specimens subjected to constant amplitude cyclic loading while containing single or multiple overloads. The residual stress and plastic damage induced by an overload are considered to be the main factors affecting the fatigue life of a specimen. The residual stress and plastic strain fields of a notched specimen are calculated using the elastic–plastic finite element method. The mean stress of the following cyclic loading is then varied by superimposing the residual stress. Meanwhile, the plastic damage is calculated based on the ductile damage model and accumulated into the total damage of the material. The quantitative effects of an overload on the damage evolution and the fatigue life are evaluated. Furthermore, the effects of the damage–overload ratio on the variation of the residual stress induced by an overload are investigated, and the effects of the occurrence time for a single overload and the occurrence frequency for multiple overloads are studied.

Dynamic finite element analysis of shot peening process of 2618-T61 aluminium alloy

Shot peening is one of the surface treatment processes usually used for the improvement of fatigue strength of metallic parts by inducing residual stress field in them. The evaluation of shot peening parameters experimentally is not only very complex but costly as well. An attractive alternative is the explicit dynamics finite element (FE) analysis having the capability of accurately envisaging the shot peening process parameters using a suitable material’s constitutive model and numerical technique. In this study, ANSYS/LS-DYNA software was used to simulate the impact of steel shots of various sizes on 2618-T61 aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The effect of shot velocity and size on the induced compressive residual stress and plastic deformation were investigated. The results demonstrated that increasing the shot velocity and size yielded in an increase in plastic deformation of the aluminium target. However, as observed, the effect of shot velocity and size was small in magnitude on the target's subsurface compressive residual stress.

A Novel Approach to Modelling Nanoindentation Instabilities

We review the recently developed models for load fluctuations in the displacement controlled mode and displacement jumps in the load controlled mode of indentation. To do this, we devise a method for calculating plastic contribution to load drops and displacement jumps by setting-up a system of coupled nonlinear time evolution equations for the mobile and forest dislocation densities by including relevant dislocation mechanisms. These equations are then coupled to the equation defining constant displacement rate or load rate. The model for the displacement controlled mode using a spherical indenter predicts all the generic features of nanoindentation such as the elastic branch followed by several force drops of decreasing magnitudes and residual indentation depth after unloading. The stress corresponding to the elastic force maximum is close to the yield stress of an ideal solid. The predicted numbers for all the quantities match experiments on single crystals of Au using a spherical indenter. We extend the approach to model the load controlled nanoindentation experiments that employ a Berkovich indenter. We first identify the dislocation mechanisms contributing to different regions of the F − z curve as a first step for obtaining a good fit to a given experimental F − z curve. This is done by studying the influence of the parameters associated with various dislocation mechanisms on the model F − z curves. The study also demonstrates that the model predicts all the generic features of nanoindentation such as the existence of an initial elastic branch followed by several displacement jumps of decreasing magnitudes and residual plasticity after unloading for a range of model parameter values. Furthermore, an optimized set of parameter values can be easily determined that give a good fit to the experimental load–displacement curves for Al single crystals of ( 110 ) and ( 133 ) orientations. Our model also predicts the indentation size effect in a region where the displacement jumps disappear. The good agreement of the results of the models with experiments supports our view that the present approach can be used as an alternate method to simulations. The approach also provides insights into several open questions.

The Influence of Plastic Deformation on the Low-Cycle Fatigue During the Burnishing of Holes in Flat Specimens of D16chT Steel

The paper deals with one of the most important problems of such closely related industries as mechanical engineering and aircraft manufacturing, involving the determination of the service life of components and structures operating under cyclic loading conditions. The presence of local structural and manufacturing stress concentrators greatly complicates the determination of the predicted life of components and structures at their design stage. The burnishing technique, namely, the method of plastic deformation of walls of the hole, aimed at achieving the amount of the residual plastic strain on their surface, is used to strengthen components with holes. The results of low-cycle fatigue tests conducted in repeating tension are presented for flat laboratory specimens of an aircraft aluminum alloy D16chT with a central cylindrical manufacturing hole hardened by burnishing. The burnisher geometry that ensures the required value of the residual plastic strain level (1, 2, and 3%) on the hole surface is calculated. The cyclic tensile loading of specimens at the stresses in a pulsating load cycle was performed in the range of 150 to 270 MPa at a frequency of 3 Hz using the equipment Bi-02-112. The influence of the amount of plastic strain in the burnished hole of the specimen on its cyclic life and fracture as a function of the load value is observed. It is found that due to plastic strain hardening of the surface of manufacturing holes, a local area of compressive residual stresses occur, causing the stress concentration around the manufacturing hole to decrease and the level of limit loads to increase. It is shown that the specimen, having a manufacturing hole hardened by burnishing (up to a plastic strain of 3%) and being cyclically loaded by a tensile stress to 170 MPa, failed not at the hole (the stress concentrator). Both the onset of the microcrack initiation and its further propagation take place in a solid region of the specimen. This is indicative that with a certain amount of residual stresses in the burnished hole, the specimen fracture under low-cycle fatigue becomes insensitive to the presence of this concentrator.

Distribution characteristics of residual film over a cotton field under long-term film mulching and drip irrigation in an oasis agroecosystem

Without an efficient mulch film recovery, the residual plastic film (RPF) causes pollution hazards to agronomic systems and natural environments. Here, we examined the distribution characteristics of RPF in the topsoils (0–40 cm) in an oasis agroecosystem in Northwest China. After cotton harvest in 2016, we collected 2304 soil samples from six cotton fields with different years of continuous mulching management (5, 9, 11, 13, 15 and 19 a). A total of 2471 pieces of RPF were separated and weighted. The weight of each RPF fragment was calibrated by its size measured in digital images. Our results showed that the amount of RPF ranged from 121.85 to 352.38 kg ha–1 across the six fields, remarkably exceeding the national standard of China (75 kg ha–1). The occurrence frequency of RPF fragments maximized at 5–15 cm depth. With the increase in soil depth, RPF fragments became smaller, and their total mass decreased linearly. After the constant mulching practice, RPF accumulated at an annual rate of 15.69 kg ha−1, mainly occurring at 0–30 cm depth. The accumulation of the larger RPF fragments (>25 mg per piece) primarily took place from 5 to 15 years after mulching started. It took over 15 years for the larger RPF fragments to degrade into smaller ones (<25 mg per piece), which accounted for 65% of the total number of RPF fragments in the field with 19-year of mulching. RPF fragments with a weight larger than 100 mg mostly concentrated at the surface (0–10 cm), whereas, the other smaller RPF fragments showed an evident downward migration. That said, with the constant mulching management, RPF pieces became more fragmented and distributed deeper, making mulch film recovery more challenging. To the best of our knowledge, this is the first time that the dynamics of RPF distribution in the soil profile after long-term mulching have been characterized. If the current mulching method continues, the accumulated RPF is going to cause severe soil pollution and risk the sustainability of the oasis agroecosystem.

Effects of Synchronous Rolling on Microstructure, Hardness, and Wear Resistance of Laser Multilayer Cladding

A synchronous rolling method was proposed to assist laser multilayer cladding, and the effects of this method on microstructure, microhardness, and wear resistance were studied. Results show that the microstructure and mechanical properties of the traditional cladding layer exhibit periodic inhomogeneity. Synchronous rolling breaks the columnar dendrite crystals to improve the uniformity of the organization, and the residual plastic energy promotes the precipitation of strengthening phases, as CrB, M7C3, etc. The hardness and wear resistance of the extruded cladding layer increase significantly because of the grain refinement, formation of dislocations, and dispersion strengthening. These positive significances of synchronous rolling provide a new direction for laser cladding technology.

Practical model of deformation prediction in soft clay after artificial ground freezing under subway low-level cyclic loading

Settlement was investigated after the long-term operation of a subway system, particularly at segments where the artificial ground freezing (AGF) method was applied in the soft clay area. In this paper, five group soil samples under different freezing temperatures (−5 °C, −10 °C, −15 °C, −20 °C, and −30 °C, respectively) were prepared to simulate different locations perpendicular to freeze tubes during one AGF circulation. Including one group of undisturbed soils, cyclic tri-axial tests were conducted on all samples, and the dynamic strains were measured and analyzed. The results show that the residual cumulative plastic strain of soft clay after artificial freeze-thaw under subway low-level repeated cyclic loading behaves quite differently from the typical Monismith’s power function development. A hyperbolic model of cumulative plastic strain of soft clay after artificial freeze-thaw is established and the relevant model parameters has been discussed for practical prediction. A critical cyclic stress ratio (CSR) of soft soil can be empirically calculated out by this practical model, only based on soil stress and soil physical state parameters without numerous cyclic tri-axial tests. All the results could provide significant reference for the safe control and environmental protection during AGF construction and subsequent subway operation.

К вопросу о реконструкции остаточных напряжений и деформаций пластины после дробеструйной обработки

Предметом исследования является математическое описание формы и напряженно-деформированного состояния стальной пластины, подвергнутой односторонней дробеструйной обработке, его экспериментальное подтверждение и применение результатов для верификации методов реконструкции полей остаточных напряжений и деформаций по экспериментальным данным. Подобная пластина используются на производстве в качестве калибровочного образца для определения времени пневмодробеструйной обработки, необходимого для формирования в поверхностном слое обрабатываемого изделия сжимающих тангенциальных остаточных напряжений заданной величины, а сам метод калибровки оказывается удобным и довольно широко распространенным для различных способов поверхностно упрочняющей обработки. Источником остаточных напряжений в данном случае является пограничный слой пластических деформаций, наводимый рассматриваемым технологическим процессом. Для постановки задачи задается структура поля тензора пластических деформаций. Форма и напряженно-деформированное состояние упругой пластины с пограничным слоем пластических деформаций были рассчитаны численно, в результате чего были выявлены качественные особенности данных полей, ослаблены граничные условия задачи и сформулированы гипотезы о структуре решения соответствующей пространственной задачи теории упругости, которое далее было найдено аналитически. Показано, что в рамках приближения плоского напряженного состояния в поперечных направлениях результат точно соответствует формуле Давиденкова - Биргера, связывающей зависимость тангенциальной компоненты остаточных напряжений от координаты по толщине пластины с функцией прогибов. Получена явная формула для зависимости остаточной (пластической) деформации от координаты по толщине. Проанализированы источники погрешностей полученных выражений и способы их коррекции. Проведен эксперимент по односторонней дробеструйной обработке калибровочной пластины, изготовленной из закаленной стали 65Г, для которой выполнено травление обработанной поверхности с измерением изменения стрелы прогиба (метод Н. Н. Давиденкова). С помощью полученных экспериментальных данных были численно реконструированы профили остаточных напряжений и деформаций с разумной точностью. Результат применим к широкому классу задач для упругих тел с упрочняющими покрытиями, а также имеет определенную методическую ценность для усовершенствования основ экспериментального исследования таких задач, позволяет формулировать и подтверждать экспериментом гипотезы о структуре решения, изучать связь рассматриваемых полей в предельных случаях, верифицировать применение различных способов учета остаточных напряжений и деформаций в численных расчетах. Найденное решение может быть использовано для верификации полей напряжений и перемещений при выборе различных вариантов предварительно напряженных или деформированных поверхностных оболочечных конечных элементов в рамках пакетов прикладных программ для расчета усталостной долговечности деталей машин с поверхностными упрочняющими покрытиями и также представляется опорным для исследования поверхностно упрочненных тел с криволинейной свободной границей, к которым сводится большинство практически важных задач.

Pulse Current Effect on the Stress-Strain State in a Cracked Steel Strip

Finite element method-based estimation results for the current pulse effect on the stress-strain state in the vicinity of the edge crack tip in a steel strip are presented. High-density reverse current along crack edges is shown to result in local stress-strain state variations near its tip, giving rise to residual plastic strains combined with thermal current-induced ones.

An Elastoplastic Finite Element Study of Displacement-Controlled Fretting in a Plane-Strain Cylindrical Contact

This work presents a finite element study of a two-dimensional (2D) plane strain fretting model of a half cylinder in contact with a flat block under oscillatory tangential loading. The two bodies are deformable and are set to the same material properties (specifically steel), however, because the results are normalized, they can characterize a range of contact scales (micro to macro), and are applicable for ductile material pairs that behave in an elastic-perfectly plastic manner. Different coefficients of friction (COFs) are used in the interface. This work finds that the edges of the contacting areas experience large von Mises stresses along with significant residual plastic strains, while pileup could also appear there when the COFs are sufficiently large. In addition, junction growth is investigated, showing a magnitude that increases with the COF, while the rate of growth stabilization decreases with the COF. The fretting loop (caused by the tangential force during the fretting motion) for the initial few cycles of loading is generated, and it compares well with reported experimental results. The effects of boundary conditions are also discussed where a prestressed compressed block is found to improve (i.e., reduce) the magnitude of the plastic strain compared to an unstressed block.