Low Thinning Research Articles

The use of MCDM techniques to assess fluid pressure on the bending quality of AA6063 heat-treated tubes

This paper investigates the bending of aluminum tubes under different fluid pressure and heat treatment conditions. The application of multi-criteria decision-making (MCDM) methods was evaluated for selecting the best forming condition considering cross-section ovality, thinning, and thickening of the bent tubes. Analytic hierarchy process (AHP) was used for criteria weighting, and technique for order of preference by similarity to ideal solution (TOPSIS) and multi-objective optimization on the basis of ratio analysis (MOORA) were used for alternative ranking. A combination of various types of AA6063 tubes, including as-received (R), annealed (O), and artificial aged (T6), with different fluid pressures (0, 1, 1.8, 3.2, and 3.6 MPa) were assumed to be as the alternatives (forming conditions). The results demonstrate that the ovality and thickening of the bent tubes decrease by increasing the internal fluid pressure. On the other hand, increasing the internal fluid pressure gives rise to an increase in thinning of bent tubes. The O sample has the lowest ovality and thickening while the T6 sample has the lowest thinning. MCDM analysis revealed that the O samples at higher pressures show better bendability.

An Investigation of the Impact of Forming Process Parameters in Single Point Incremental Forming Using Experimental and Numerical Verification

Incremental sheet forming (ISF) is an innovative cold forming operation and has enticed great interests owing to its flexibility and capability to manufacture various complex 3D shapes with low costs and minimum requirements. Single point incremental forming (SPIF) is the most popular type of ISF process and has high quality and less occurrence of defects for the formed products if the operating parameters are achieved and evaluated with high precision. In this study, the impact of tool diameter and forming angle on the forming force, thickness distribution, thinning ratio, effective plastic strain, forming depth and fracture behaviour was explored. AA1050 aluminium alloy and DC04 carbon steel were employed to produce a truncated cone in accordance with the SPIF process. A 3D finite element model was required to achieve a well-established investigation. The SPIF of a truncated cone numerical model was adopted to build a model with the same conditions as of the experimental work with aid of ANSYS software version 18 through using the workbench LS-DYNA model. The sheet metal modelling was carried out in accordance the Cowper Symonds power law hardening by taking the behaviour of the material as elastic–plastic, and the anisotropic properties were assumed to simulate the plasticity behaviour for two sheet metals. Results indicate that the DC04 carbon steel has a higher forming force, minimum thickness and lower thinning ratio compared with AA1050 aluminium alloy under the same operating conditions.

Experimental and simulation studies on hybrid incremental sheet forming

In the present research work, parts are formed using two-step hybrid incremental sheet forming (HISF) process. The effect of process parameters such as preform tool size, tool diameter, and preforming depth on thinning in the formed part is studied. A simulation model is developed and simulation results are compared with the experimental results. Also, results of HISF process are compared with the results of single point incremental sheet forming. The simulation results are in good agreement with the experimental results. It is observed that HISF process results in lower thinning as compared to SPIF process. Further, it is found that preform tool size has considerable influence on the minimum thickness of formed part. Large preform tools result in relatively lower thinning.

Forest thinning and organic matter manipulation drives changes in soil respiration in a Larix principis-rupprechtii plantation in China

Plantation management practices may influence carbon dioxide (CO2) uptake dynamics; however, the responses of carbon losses, such as soil respiration, to management (e.g. thinning) have not been sufficiently studied. We evaluated the effects of forest thinning (no thinning (NT), low thinning (LT), medium thinning (MT), and high thinning (HT) and organic matter manipulation (intact soil (untreated control, UC), exclusion of aboveground litter (EL), and exclusion of both aboveground litter and roots (ELR)) on soil respiration in a Larix principis-rupprechtii plantation. During the period from 2015–2018, soil respiration was continuously monitored from May to October (growing season). Meanwhile, soil temperature and soil moisture at a depth of 5 cm were also measured. In addition, three soil samples were collected to measure biochemical properties of soil. We found that mean soil respiration (Rs) was significantly greater in MT than that in NT (by 21.5 %). RS in HT was significantly greater than NT in 2015 (by 25.0 %) and then finally lower than NT (14.8 %) in 2018. However, RS in LT compared with NT showed no response to thinning during our observation period. The organic matter manipulation also affected soil respiration. Mean reduction of soil respiration in EL (REL) and in ELR (RELR) compared to Rs ranged from 25.9%–39.2% and 40.8%–53.6% across all thinning regimes, respectively. The temperature sensitivity (Q10) values of RS, REL, RELR ranged from 2.23 to 2.72, 2.21–2.60, and 2.31–2.90, respectively. The model with the best fitting temperature and moisture factors explained 63.8 % - 75.4 % changes in RS, 65.9 % - 74.7 % changes in REL and 70.4 % - 74.1 % changes in RELR. Stepwise regression analyses showed that soil temperature, ratio of soil carbon and nitrogen in the topsoil explained the pattern of RS across the thinning scenarios. REL showed a high sensitivity to changing in some soil chemical properties and hydrolases activities, whereas RELR showed a high sensitivity to changing in microbial activity combined with temperature and pH of soil. Overall, our data show that the response of organic matter inputs to thinning has an important impact on soil CO2 fluxes of plantation, and emphasize the difference of the response between aboveground and underground organic matter inputs to soil CO2 fluxes.

Soil ecoenzymatic stoichiometry and microbial resource limitation driven by thinning practices and season types in Larix principis-rupprechtii plantations in North China

The extracellular ecoenzymatic stoichiometry (EES) of the soil are key indicators of the nutritional status and relative resource limitations of microbes that play important roles in biogeochemical cycling and ecosystem functions. However, our knowledge of the effects of forest thinning and the seasons on the variability of extracellular ecoenzymatic activities (EEA) and EES in the soil is limited. We examined the soils from Larix principis-rupprechtii plantations after nine years of treatments with four different thinning intensities (i.e., control (CK), low thinning (LT), moderate thinning (MT), and high thinning (HT)) in four different seasons. We measured the activities of one carbon (C) acquiring enzyme (β-1,4-glucosidase (BG)), two nitrogen (N) acquiring enzymes (β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP)), and one phosphorus (P) acquiring enzyme (acid phosphatase (AP)), and examined potential factors (soil environment, nutrients, and microbial biomass) that may influence the activities of these enzymes. Our results showed that thinning significantly (p < 0.05) enhanced the activities of the BG, NAG + LAP, and AP. The EEA were higher in summer and autumn than those in spring and winter. Further, MT and HT stands exhibited lower BG:(NAG + LAP) and higher (NAG + LAP):AP ratios than the CK and LT stands, demonstrating that MT and HT caused a greater N limitation for soil microbes. The higher (NAG + LAP):AP ratio during winter indicated that the microbial N limitation was increased in this season. The variations in the EEA, EES, environment, nutrients, and microbial biomass in the soil among different thinning treatments demonstrated that thinning could markedly promote microbial activities and metabolism and improve nutrient cycling. Based on analyses of the BG:(NAG + LAP) ratio, (NAG + LAP):AP ratio, and the threshold element ratio, we found that the metabolism of soil microbes was limited by N in L. principis-rupprechtii plantations in North China. A redundancy analysis and a variation partitioning analysis revealed that variations in the EEA and EES of soils could attributed to the alterations in soil properties, especially soil nutrient and microbial biomass. Overall, the ecoenzymatic C:N:P stoichiometry was dependent on the resource availability in the soils rather than on homeostatic mechanisms. Our research highlights the importance of the effects of thinning practices and season types on ecoenzymes and microbial metabolism, and provides insights into the microbial resource limitation, nutrient cycling, and ecological processes in plantation forests after thinning.

Optimization of Processing Parameters for a Reverse Drawing–Flanging Combined Process for a B550CL High-Strength Steel Spoke Based on Grey Relational Analysis

Undesired wall thickness distribution and flanging cracking easily occur in reverse drawing–flanging combined processes of steel spokes when improper process parameters are used. Thus, based on GRA (grey relational analysis) and FEM (finite element method), a GRA model for a reverse drawing–flanging combined process for high strength steel B550CL spoke was established and validated. The results show that: (1) the most significant factors affecting uneven wall thickness distribution and excessive thinning in the mounting zone and center hole cracking are the friction coefficient and the shape of punch, respectively; (2) the non-uniformity of wall thickness U increases with the increase of the friction coefficient. The conical punch has a lower thinning ratio T, the spherical punch has a lower value of damage D; (3) considering synthetically the indexes of uneven wall thickness distribution, the excessive thinning in the mounting zone and center hole cracking, optimal results for the process parameters are obtained.

Numerical and experimental investigations of hydro-mechanical deep drawing process of laminated aluminum/steel sheets

The application of hydro-mechanical deep drawing (HMDD) process on laminated sheets combines advantages of both process and material to improve the forming condition of poor formable light-weight metals such as aluminum alloys. In this research, the HMDD process of anisotropic laminated bimetallic sheets has been analyzed using a 3D finite element simulation with implementing Fortran based code for accurate modeling of non-uniform oil pressure distribution. To verify FE results, experimental works were conducted on the widely used laminated aluminum/steel sheets. Based on the developed FE model, parametric studies were performed to investigate the effect of material parameters such as layers thickness and lay-up arrangement on the forming condition, process window and formability of aluminum sheet as key process parameters. Results demonstrated that suitable process condition to attain a successful forming of bimetallic aluminum/steel sheets can be predicted by developed FE model reasonably. Also, It shown that wider working zone was achievable with decrease in drawing ratio, reduction in thickness of sheet with lower strength layer and also when aluminum sheet is in contact with punch (A/S lay-up). In addition, the higher limiting drawing ratio (LDR) and lower thinning in low formable aluminum sheet would be achievable in A/S lay-up than S/A lay-up.

Determination of Proper Loading Profiles for Hydro-Mechanical Deep Drawing Process Using FEA

Hydro-mechanical Deep Drawing (HMD) is an advanced manufacturing process developed to form sheet metal blanks into complex shapes with smooth surfaces using hydraulic pressure as an additional source of deformation force. There are many factors affecting the successful production of desired parts using this manufacturing process. The most important factors are the fluid pressure and blank holder force. Having proper values of these parameters during forming has a direct impact on part properties such as drawing ratio and thinning. In order to determine desired the fluid pressure and blank holder force profiles, which are different for every geometry, material and other process conditions, finite element simulations are conducted to save time and cost. Abaqus FEA software is used in this study. In order to define the continuously changing fluid pressure application area on the sheet material, which is not an available module or standard interface of software, sub-programs (sub-routines) are developed to properly and dynamically define the fluid pressure area. Proper, if not optimal, fluid pressure and blank holder force profiles, which allow the formability (LDR) of sheet material to be maximum, were obtained using trial and error method. Maximum thinning values on metal blank were used as a control parameter to determine if selected loading profiles result in the highest LDR with lowest thinning.

Type and Timing of Thinning Hybrid Poplar Coppice Affects Growth

Abstract To optimize the growth of a hybrid poplar coppice plantation, a thinning trial was established in eastern Ontario. Four treatments were investigated: (1) thinning stools to one dominant sprout with residuals clipped at a height of 1 m (to increase operational efficiency of thinning), (2) thinning to one dominant sprout with residuals completely removed, (3) thinning to three dominant sprouts with residuals completely removed, and (4) no thinning. All treatments were performed at the beginning of either the third or fifth growing seasons (timing treatment one and two, respectively). When the 7-yr-old data were analyzed (i.e., 5 growing seasons after timing treatment one and 3 growing seasons after timing treatment two), thinning did not increase dominant sprout growth and significantly larger quantities of wood fiber were produced with lower thinning intensities or no thinning because of the greater number of sprouts per stool. Results of this trial suggest there is no advantage to thinning hybrid poplar coppice after the beginning of the third growing season. North. J. Appl. For. 8(4):166-168.